have eyes in the back of your head
have eyes in the back of (one's) head
To be or seem to be able to detect what is going on all around one, even beyond one's field of vision. My mom always seems to know when we've done something naughty. She has eyes on the back of her head! Look, just be very careful not to do personal things during the work day—the boss has eyes on the back of his head.
have eyes in the back of your headobserve everything that is happening even when this is apparently impossible.
1991 Barbara Anderson Girls High They were all in Miss Royston's class who said that she had eyes in the back of her head and they half believed it, because how else did she know.